The Bakker-Arkema model for grain drying in deep beds was modified to simulate the process of coffee drying using a proposed thin-layer equation that had been adapted for parchment coffee. A proposed empirical thin-layer model was incorporated into the deep-bed coffee drying model. A prototype coffee-bean drying bin was tested in the Agricultural Experimental Station in Adjuntas, Puerto Rico, and used for validation of the mathematical model. The model predicted the moisture level of the beans with a maximum deviation of 3 (w.b.) throughout the drying process. The airflow direction was reversed in 3- or 6-hour intervals, and the drying air temperature was 55 ℃. The initial moisture content was 55 to 56 (w.b.). Twenty-seven hours were needed to reach a moisture level of 11 w.b. using an airflow rate of 15.24 m{sup}3 m{sup}(-2) min{sup}(-1).
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